Humans have been living in orbit, on and off, since 1971, and without a single day's break since November 2000. The International Space Station made that streak possible, but it is now in its final years, with a deorbit vehicle under contract and successors racing to be ready. This guide covers the whole arc: why stations exist, the ones that came first, how the ISS works, and what flies next.
Why put a laboratory in orbit?
Sustained microgravity is the one condition no lab on Earth can fake for more than seconds. Aboard a station, flames burn as spheres, fluids behave without buoyancy, protein crystals grow more perfectly for drug research, and the Cold Atom Lab chills atoms into quantum states. Just as important is the medicine: NASA's Twins Study compared Scott Kelly's 340 days in orbit against his identical twin on the ground, and the station's life support now recycles about 98 percent of the water crews use, a number that has to hold before anyone attempts a multi-year Mars voyage.
The first generation: Salyut, Skylab, and Mir
The Soviet Union flew the first station, Salyut 1, in April 1971, opening the era of living and working in space. America answered with Skylab in May 1973, hosting three crews and proving people could work in orbit for months. The decisive step was Mir, whose first module launched in February 1986: assembled piece by piece over a decade, it became the first long-duration modular outpost and set endurance records that stood for decades. Every station since, including China's, follows Mir's modular blueprint. The timeline traces each of these milestones.
How does the ISS work?
The ISS is a partnership of five agencies (NASA, Roscosmos, ESA, JAXA, and Canada's CSA) representing 15 nations. Assembly began with the Zarya module in November 1998 and took more than 40 flights; the finished station spans 109 meters, masses about 420 tonnes, and circles Earth every 90 minutes at roughly 400 kilometers. It has been continuously occupied since November 2, 2000, hosted more than 280 visitors, and required over 270 spacewalks to build and maintain. It is also regularly visible from your backyard as one of the brightest objects in the night sky.
Who flies there, and how?
Crews originally rotated on the Space Shuttle and Russia's Soyuz, which became the only ride after the shuttle retired in 2011. NASA's Commercial Crew Program ended that dependence: SpaceX's Dragon has flown operational rotations since 2020, while Boeing's Starliner has yet to carry an operational crew and its next flight was converted to an uncrewed cargo run. Supplies arrive on cargo Dragons, Northrop Grumman's Cygnus, Russia's Progress, and Japan's HTV-X. A seat-barter arrangement keeps crews integrated: cosmonauts fly on Dragon while NASA astronauts fly on Soyuz.
When does the ISS come down?
The Western partners have committed to operate the station through 2030, Russia through at least 2028. NASA awarded SpaceX a contract worth up to 843 million dollars for the US Deorbit Vehicle, an enlarged Dragon derivative with 46 thrusters that will dock around 2029 and, after a period of natural orbital decay, steer the complex into a remote stretch of ocean in late 2030 or early 2031. The date is not settled politics: a draft measure in the US Senate would direct NASA to keep the station flying through 2032, reflecting worry that no replacement will be ready in time.
What replaces it?
One successor is already flying: China's Tiangong, assembled in 2021-2022 from three modules and permanently staffed by three-person crews, built after US law excluded China from the ISS partnership (see CNSA). On the commercial side, NASA's Commercial Low Earth Orbit Destinations program funds Axiom Space (which plans to attach modules to the ISS before free-flying), Starlab, and Blue Origin's Orbital Reef. The nearest-term entrant is outside that program entirely: Vast's privately funded Haven-1, a single-module station slated to launch on a Falcon 9 in the first quarter of 2027, which would make it the first commercial space station if it holds schedule.
Frequently asked questions
How many space stations are in orbit right now?
Two: the International Space Station and China's Tiangong. Both are permanently crewed.
How long have humans lived in space without a break?
Continuously since November 2, 2000, when Expedition 1 boarded the ISS. The streak passed 25 years in November 2025, and Tiangong adds a second uninterrupted human presence.
What happens to the ISS at the end of its life?
A SpaceX-built US Deorbit Vehicle will dock with the station around 2029 and perform a final burn in late 2030 or early 2031, bringing it down over an unpopulated stretch of ocean. A Senate proposal to extend operations to 2032 could shift that schedule.
Can private citizens visit a space station?
Yes, at a price. Soyuz carried the first paying visitors from 2001, and Axiom Space has flown private and government-sponsored crews to the ISS on Dragon since 2022, with seats reported around 55 to 70 million dollars. See space tourism for the full history.